Transparency positioner for projector stage



United States Patent l l l Inventor Robert A. Klein Skokie, IllinoisApp1.No. 711,427 Filed March 7, 1968 Patented Nov. 24, 1970 AssigneeBell & Howell Company Chicago, Illinois a corporation of IllinoisTRANSPARENCY POSITIONER FOR PROJECTOR STAGE 6 Claims, 3 Drawing Figs.

U.S. Cl 353/122;

' 33/180z353/66 Int. Cl ..G03b 21/00 Field oiSearch 355/72, 74;

353/37, 50, 66, 73. 77,122. 22: 33/|84.5. 180A, 181, 189, l74TB; 269/315References Cited UNITED STATES PATENTS 10/1932 Dreifuss 33/76 5/1961Andrisani 33/1845 8/1966 Abbott et al. 353/24 9/1967 Zollner 353/66X5/1968 Ploch etal. 33/184.5X

Primary Examiner-William D. Martin, .Ir. A!t0rneyWilliam F. Pinsak andJohn E. Peele Jr.

ABSTRACT: A transparency positioner is provided for locating the centerof any of several sizes of transparencies substantially over the opticalcenter of an overhead projector stage. The positioner has L"-orientedlegs, in one of which legs, aligning holes are provided to enableselective positioning of the positioner on locators secured in the stagefor proper positioning of the size oftransparency to be projected.

TRANSPARENCY POSITIONER FOR PROJECTOR STAGE This invention relates to awork organizer adapted for use on an overhead projector stage, andparticularly relates to structure for properly positioningtransparencies on the stage.

Overhead projectors have gained much popularity in schools andbusinesses because they permit' the user to project large sizedtransparencies. These transparencies have the advantage that the can beprepared on-the-spot". After preparation these transparencies, with orwithout mounts or frames, are placed on the stage of an overheadprojector. Usually, an image receiving surface such as a screen ispositioned before the audience to receive an image projected from thetransparency. However, because of the lack of a work or ganizer, such asa transparency positioner, the transparencies are often projected sothat their image falls outside the area defined by the screen. Othertransparencies may be skewed with respect to horizontal and verticalalinement relative to the edges of the screen. Still othertransparencies may be substantially offcenter of the screen. Further,when different sized transparencies are used, the alinement from onesize to another may shift back and forth over the screen. Such errors inprojection, whether or not corrected, disturb the concentration of theaudience.

The transparency positioner of the present invention is constructed asan L-shaped plate having a plurality of alining openings in one of thelegs of the L. These openings are spaced relative to the interior edgeof the leg so that the locator may be variably positioned relative tolocators on the stage of the optical apparatus. By properly orientingthe positioner, a transparency to be positioned on the stage an beabutted against the inner edges of the positioner, and thereforeproperly alined relative to the optical center of the stage. Byadjusting the positioner so that other sets of aliners seat on thelocators fixed to the state, other sizes of transparencies may be justas easily and properly oriented on the stage.

With the instant positioner, the projectionist can continually face theaudience while accurately positioning each of several transparencies.The image is alined both vertically and horizontally without requiringextreme care in locating the transparency.

Thus, an object of the present invention is to provide a transparencypositioner device to properly orient transparencies on the stage of anoverhead projector.

Another object of the invention is to provide a transparency positioneradapted for selective orientation on the stage of an overhead projector'so as to aid in properly alining any of several sizes of transparencieson the stage.

Still another object is to provide a transparency positioner having apair of legs, in one of which are a plurality of alining means intendedto cooperate with locators on the projector stage whereby transparenciesare accurately positioned.

Further and other objects will be apparent from the followingdescription when read with the accompanying drawings in which likenumerals refer to like parts.

In the drawings:

FIG. 1 is a perspective view of an optical apparatus having atransparency positioner positioned on the stage thereof;

FIG. 2 is an enlarged plane view ofthe positioner, and a typicaltransparency shown segmentally; and

FIG. 3 is an enlarged perspective view in partial section disclosingdetails of the locator and aliners on the stage of the apparatus.

Referring to FIG. 1, an optical instrument 10, such as an overheadprojector, is shown. This preferred embodiment of the instrument has abase 12, adapted to contain a light source (not shown). Thesubstantially horizontal upper surface of base 12 is defined as a stage16 on which a transparency 20 is positionable. The operative portion ofthe stage is formed ofa transparent plate 22, made of glass or plastic,and supported over an opening in the base through which light passes toand through transparency 20. Usually, this plate 22 is formed ofaFresnel lens to concentrate the light rays so as to better illuminatethe full dimensions of transparency 20.

A typical transparency 20, seen segmentally in FIG. 2, is prepared byforming an opaque image 26 on an otherwise transparent image supportmaterial 28. Although this support material may be laid directly onplate 22, in this preferred embodiment, the support material 28 is shownmounted in frame 30, having edges 32. This frame enables the operator oruser of the instrument to move the transparency to and from stage 16without touching the to-be-projected image area thereof. Commercially,frames are available in but a few predetermined rectangularconfigurations insofar as their outside dimensions are concerned. Theframes may have many interior configurations. However, the exteriordimensions usually center the image support material so that the centralimage portion is substantially over the center of plate 22 when thetransparency is correctly positioned on the stage.

In FIG. I, a projection head 34 is seen supported above stage 16 of theprojector by an upright post 36. For purposes of illustration only,since many head configurations are to be found in the market place, thehead is defined by at least one image projecting objective 40, and amirror 42. The optical axis of projection head 34 is generally alinedwith a vertical optical path 46, which extends from substantially thecenter of plate 22 and stage 16. As the image passes into head 34 eitherthrough objective 40 or an aperture in its place, the image is reflectedby mirror 42 to exit from the head substantially horizontally alongoptical path 50. Mirror 42 may either receive an image focused byobjective 40 and reflect that image through an image exit opening 52 inthe head, or it may receive a substantially nonfocused image through anopening in place of objective 40 and reflect it through an objectivelocated at 52. Obviously, objectives may be incorporated in both theposition of objective 40 and objective 52. After the image exits alongoptical path 50, it is projected onto a screen or other image receivingsurface (not shown).

A transparency positioner 60 is proposed to ensure alinement of thecenter of transparency 20 over the optical center of stage 16. Near theperiphery of stage 16 and adjacent plate 22, a pair of locators, such aspins 64, are fixed in the stage and spaced a predetermined distance onefrom another. The positioner is preferably formed as a plate of sheetmaterial defining a pair of legs 60a, 60b oriented in L fashion, andparticularly defining a pair of interior edges 62, angledperpendicularly one to another. Typically, this sheet material may beany of the substantially rigid plastic materials not subject todeformation by the heat transmitted from the projection lamp of theapparatus. In one of the legs, a plurality of pairs of aliners, such asholes 66a-h, 67a-h are formed. The holes defining each pair of alinersare spaced from one another a distance substantially equal to thespacing between the locator pins 64. In this preferred embodiment onehole of each pair is circular, and of a dimension to seat snugly on theappropriate pin 64. The other hole is formed as a small oval to enablequick orientation of the positioner on the pins 64 which extend upwardlyfrom the stage. The slight oversize of this latter hole also permitsinterchange of the organizer on various projectors which may not havethe precise pin alinement required if only two circular holes were used.

Each pair of holes 66a-h, 67a-h disclosed as connected by a line 70, isformed so as to orient the positioner to properly position atransparency having a particular external configuration. Typically, thepreferred embodiment provides for alinement of transparencies having thefollowing external dimensions: (in inches) 11x9 10%;:12 10x8 9x11 8X88x10 7x7 Obviously, other transparency sizes may be taken intoconsideration and holes prepared therefor. To prepare such other holes,the transparency i s positioned with its center over the optical centerof plate 22. Positioner 60 is then oriented to bring interior edges 62into engagement with the edges of the transparency. The holes may thenbe formed in the leg 60b of the positioner for alinement on locator pins64. The operator can then project this size transparency as readily asthe prepared sizes of transparencies.

From the description of the foregoing embodiment of the invention itwill be seen that a transparency positioner is provided which ensuresproper positioning ofa transparency over the optical center of anoverhead projector stage. In use, the operator merely determines theexternal size of the transparency to be used. Next, he orients thepositioner to seat the proper holes over the pins on the stage. A seriesof transparencies of a given external configuration may then be placedwith their edges in abutting relation with the interior edge of thepositioner wherein substantially alined over the optical center of thestage. When a new transparency size is to be used, the operator needsonly to determine its size, and reorient the positioner beforeproceeding.

It is to be understood that the embodiment shown is illustrative of theprincipal operation of a transparency positioning device and thatcertain changes, alterations, modifications or substitutions may be madeto the structure of the device without departing from the spirit andscope of the invention as set forth in the appended claims.

I claim:

l. A transparency positioner for use with an overhead projector having aprojection stage, the positioner being usable to orient different sizedtransparencies on the stage, the positioner comprising:

a plate member having a pair of leg portions in L orientation, said legportions having predetermined internal edges; and

at least two pair of aliners in one of said leg portions to cooperatewith a fixed pair of locators on said stage their respective centerswill be wherein a particular sized transparency is substantially alinedover the optical center of said stage when one of said pair of alinerscooperates with said locators to orient said positioner, and to orient atransparency when said transparency substantiallyabuts both saidinternal edges otsaid positioner.

2. A positioner as in claim 1, wherein said aliners are holes, and saidlocators are pins extending above the stage, said holes cooperating withsaid pins to orient said positioner on the stage.

3. A positioner as in claim 1 wherein said aliners are positioned insaid leg portion relative to said internal edge of said positionerwherein both said interior edges are oriented to predetermined positionsrelative to said optical center of stage.

4. A positioner as in claim 3 wherein said interior edges of said legsare oriented perpendicular to one another.

5. A positioner as in claim 1 wherein said aliners of each pair arespaced apart the same distance, and said locators on said stage arespaced apart an equal distance.

6. In combination with an overhead projector having a stage on which asubstantially rectangular transparency is positionable for projection,the invention comprising:

at least a pair of spaced alining pins secured in said stage andextending upwardly therefrom; and

a transparency positioner locatable on said stage; said positioner beingformed of sheet material with a pair of legs, the inner edges of whichlegs are perpendicular to one another, and having at least a pair ofequally spaced holes in one of said legs for positioning over said pinson said stage; said spaced holes being formed in said positioner whereinengagement of the edges of said rectangular transparency on the edges ofthe positioner causes alinement of the center of said transparencysubstantially over the optical center of the stage.

